1. Field of the Invention
This invention relates to data networks. More particularly, this invention relates to the identification of different devices on a network, which share a common network address.
2. Description of the Related Art
TABLE 1Acronyms and AbbreviationsNATNetwork Address TranslationIPInternet ProtocolIPIDIP IdentificationRDRReport Data Record
For a computer to communicate with other computers or servers within a packet-switched network, e.g., the Internet, the computer must have a unique IP address. IP protocol version 4 specifies 32 bits for the IP address, which theoretically gives about 4,294,967,296 unique IP addresses. However, in practice there are actually only between 3.2 and 3.3 billion addresses available, due to reservation of some of the IP addresses for multicasting, testing and other special uses. Due to growth of the Internet, the number of IP addresses is now insufficient.
One solution for increasing the utility of the limited number of IP addresses is referred to as network address translation (NAT). NAT allows an intermediary device, e.g., computer, router or switch, which is located between the Internet and a local network, to serve as an agent for a group of local computers or devices. A small range of IP addresses or a single IP address is assigned to represent the local group. Each device within the local group is also given a local IP address that is only used within that local group. The local group's local IP addresses may duplicate IP addresses that are used within another local network. However, due to their limited scope, local IP addresses of different local groups do not conflict. When a local computer attempts to communicate with a remote computer situated outside the local network, the intermediary device matches the local computer's local IP address to one of the intermediary device's assigned IP addresses. The intermediary device then replaces the local computer's local address with the matched assigned IP address. The matched assigned IP address is then used to communicate between the local computer and the remote computer. Typically, a NAT device intercepts packets and performs network address translation prior to forwarding them via facilities of an Internet service provider to the intended recipient.
A new protocol, Internet Protocol Version 6 (IPv6), promises an IP address space that exceeds the connectivity needs of the foreseeable future. However, IPv6 is still in its early phases of deployment. Currently, enabling a community of clients within an enterprise to be uniquely addressable is typically accomplished through NAT. In general, the more devices that share an IP address, the more bandwidth of an Internet service provider must be allocated to that address. In order to optimize use of its facilities, and to ensure compliance with contractual terms, e.g., the number of devices permitted to use an internet connection concurrently, it would be desirable for the Internet service provider to know how many devices are concurrently active behind a NAT unit.